Photodissociation of NO2 in the (2) (2)B2 state: the O((1)D2) dissociation channel.
Photodissociation of NO2 in the (2) (2)B2 state: the O((1)D2) dissociation channel.
复制标题
DOI：
10.1063/1.3194286
复制
发表时间：
2009-08
期刊：
影响因子：
--
通讯作者：
I. Wilkinson;M. P. de Miranda;B. J. Whitaker
中科院分区：
文献类型：
--
作者：
I. Wilkinson;M. P. de Miranda;B. J. Whitaker
利用直流切片和粉碎速度图成像技术研究了二氧化氮在第二解离极限以上的光解离动力学。这篇论文是之前一篇论文的姊妹篇[J]。化学。其中，我们报道了O((3)P(J)) + NO(（2)Pi(Omega)）绝热产物通道的结果。在这里，我们研究了在类似激发能下的O((1)D(2)) + NO(（2)Pi(Omega)）非绝热产物通道。通过单色和双色成像实验分别观察了状态选择的NO碎片和O原子的速度分布，我们能够建立一个详细的解离动力学图像。我们表明，通过将从速度图成像研究中获得的信息与质量分辨共振增强多光子电离光谱相结合，可以解释和充分分配NO图像。通过记录O(1)D(2)光碎片在泵浦和探针激光场不同偏振组合下的双色图像，我们还测量了原子碎片中的轨道角动量对准。我们发现整个O(1)D(2)光碎片分布与M(J) = +/-1磁性亚能级中的大多数种群相似。碎片极化的相似性被解释为所有的O(1)D(2)原子都是通过相同的避免交叉形成的。在光解能为5.479 52 eV时，NO碎片优先在v = 1处形成，振动激发的碎片呈现双峰旋转分布。这与v = 0时NO碎片的单峰旋转剖面形成对比。我们根据绝热势能面计算拓扑讨论了这些观察结果，并将v = 1碎片的振动反演和旋转双峰性归因于(2)(2)B(2)态激发时产生的对称拉伸和弯曲运动。
Direct current slice and crush velocity map imaging has been used to probe the photodissociation dynamics of nitrogen dioxide above the second dissociation limit. The paper is a companion to a previous publication [J. Chem. Phys. 128, 164318 (2008)] in which we reported results for the O((3)P(J)) + NO((2)Pi(Omega)) adiabatic product channel. Here we examine the O((1)D(2)) + NO((2)Pi(Omega)) diabatic product channel at similar excitation energies. Using one- and two-color imaging experiments to observe the velocity distributions of state selected NO fragments and O atoms, respectively, we are able to build a detailed picture of the dissociation dynamics. We show that by combining the information obtained from velocity map imaging studies with mass-resolved resonantly enhanced multiphoton ionization spectroscopy it is possible to interpret and fully assign the NO images. By recording two-color images of the O((1)D(2)) photofragments with different polarization combinations of the pump and probe laser fields we also measure the orbital angular momentum alignment in the atomic fragment. We find that the entire O((1)D(2)) photofragment distribution is similarly aligned with most of the population in the M(J) = +/-1 magnetic sublevels. The similarity of the fragment polarizations is interpreted as a signature of all of the O((1)D(2)) atoms being formed via the same avoided crossing. At the photolysis energy of 5.479 52 eV we find that the NO fragments are preferentially formed in v = 1 and that the vibrationally excited fragments exhibit a bimodal rotational distribution. This is in contrast to the unimodal rotational profile of the NO fragments in v = 0. We discuss these observations in terms of the calculated topology of the adiabatic potential energy surfaces and attribute the vibrational inversion and rotational bimodality of the v = 1 fragments to the symmetric stretch and bending motion generated on excitation to the (2) (2)B(2) state.